Monday, July 15, 2024 Detailed Auto Topics
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A rough idle and poor fuel mileage means the vehicle needs a tune up. Once, this may have been so, but it is not true anymore. A ‘tune-up’ will not fix these issues on any modern vehicle or show any performance improvement.

A tune up saves damage, it will not fix a running problem 

Many years ago, mechanical systems closely tied the performance of a vehicle to the condition of ignition components. Today, the power control module or PCM can make allowances for wear. For example, as the spark plugs fire, metal slowly wears from the electrodes. This increase in the plug gap would cause the spark to weaken. Today’s engine control system simply increases the duty cycle and the plug continues to fire normally. The driver will notice no decrease in performance or fuel mileage, even with badly worn plugs.

If it is not broken, why fix it?

So why would we ever need to replace the spark plugs? The answer is to prevent problems. As the duty cycle continues to increase, the secondary ignition works much harder. Coil failure results as the components become overworked. The expense of replacing ignition coils is far greater than spark plugs. We replace the plugs to prevent such damage. With a tune up, the driver will notice no increase in performance.

Clearly, vehicle owners do not like their vehicles to run poorly. Auto makers program the PCM to hide symptoms from the driver. A rough idle or lowered fuel mileage results from problems beyond computer control. When a sensor goes bad or a mechanical component fails, the computer is no longer able to control things. This is when the driver notices symptoms. To help prevent this, we do maintenance, such as the tune up.

Manufacturers may confuse people unnecessarily

To make a vehicle more attractive at the time of purchase, car makers extend maintenance intervals to the maximum. Many salespeople carry this even further, insinuating the vehicle needs no service. Fewer things need attention on modern vehicles, but those things that do are critical. Many breakdowns we see, result from this lack of maintenance. As above, worn spark plugs result in bad coils. Worse, a failed coil can damage the catalytic converters. Missing needed maintenance results in a major repair.

Cars need maintenance now, more than ever before

Another example is a proper transmission service. Car salespeople tell some buyers their transmission never needs service or that manufacturers seal it. This is not so and a restricted filter will cause transmission problems. Best is to read thoroughly the owner’s manual for the vehicle, or go to a trusted professional for advice. We recommend a General Inspection, once a year, to prevent problems. This simple service will help keep from missing important services and help prevent breakdowns.

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